1. Field of Invention
The present invention relates to a receptacle-type bi-directional optical module.
2. Description of Related Art
Optical sub-assemblies (OSA) in an optical communication system can be classified as transmitter optical sub-assemblies (TOSA) or receiver optical sub-assemblies (ROSA) according to devices with different functions. The transmitter optical sub-assemblies are capable of optically coupling laser diodes or light emitting diodes to an optical fiber, such that electrical signals can be transformed to light signals and be focused by lens to be transmitted in the optical fiber. On the contrary, the receiver optical sub-assemblies are capable of optically coupling the light signals in the optical fiber to pin diodes or avalanche photodetector (APD) by being focused with lens, so as to transform the light signals to electrical signals. A so-called bi-directional optical sub-assembly (BOSA) integrates a transmitter optical sub-assembly and a receiver optical sub-assembly in a single sub-assembly and executes functions of transmitting and receiving with a single optical fiber.
Optical fibers that can be used for transmitting light are made of glass fibers or plastics fibers. The diameter of an optical fiber is only about 10 um, which is just a bit thicker than a hair. By being encapsulated into the plastic cladding, the optical fiber can be bent without breaking. Compared with the conventional cable, the optical fiber have advantages such as high bandwidth, large communication capacity, less decay, far transmitting distance, small crosstalk, high transmission quality, resistance to electromagnet interference, high secrecy, small size, lightness, ease of laying and removing, abundant information, etc. Therefore, the optical fiber is good enough to substitute for the conventional cable to be the medium for communication transmission.
Although there are many advantages and characteristics, the optical fiber has some disadvantages. Please refer to FIG. 5. FIG. 5 is a stereoscopic view showing that a conventional pigtail-type BOSA 42 connects to an optical connector 40 through an optical fiber 44. The pigtail-type BOSA 42 is easy to be damaged during manufacturing processes. Besides, the optical fiber 44 must be orderly entwined when the pigtail-type BOSA 42 is disposed on the circuit board, as shown in FIG. 5. But, the terminal processing of the optical fiber 44 is hard to be handled, operations of splitting and coupling are complicated, and etc. Especially, the optical fiber 44 is brittle and has low mechanical strength, so the bending radius of the optical fiber 44 is not proper to be too small. Moreover, if the pigtail-type BOSA 42 is directly welded on the circuit board, the heat dispersing performance will becomes worse.